1. Field of the Invention
The present invention relates to a solenoid-type fuel injection valve mainly for use in a fuel supply system in an internal combustion engine, and particularly to an improvement of a solenoid-type fuel injection valve comprising a valve seat member having a valve seat and a valve bore provided through a center portion of the valve seat, a valve stem for opening and closing the valve bore by cooperation with the valve seat, an injector plate coupled to an outer end face of the valve seat member and having a plurality of fuel injection bores disposed around an axis of the valve bore, and a fuel diffusion chamber which is defined between the valve seat member and the injector plate and which is faced by the valve bore and all of the fuel injection bores, the plurality of fuel injection bores being parted on a plane including the axis of the valve bore into primary and secondary groups for injecting fuel toward a pair of primary and secondary intake ports, respectively.
2. Description of the Related Art
Such a solenoid-type fuel injection valve is already known, for example, as disclosed in Japanese Patent Application Laid-open No. 2000-97129.
In such known fuel injection valve, the fuel injection bores are provided in the injection plate, so that they are inclined to become farther radially from the axis of the valve bore at a more downstream location, and the angles of fuel spray foams formed by the fuel flows injected from all the fuel injection bores are set depending on such inclination angles.
When the fuel injection bores are provided in the injection plate, so that they are inclined to become farther radially from the axis of the valve bore at the more downstream location, the directions of inclination of the fuel injection bores are different in two directions (a direction of arrangement of the pair of intake ports and a direction perpendicular to the direction of arrangement). For this reason, it is not easy to make the fuel injection bores and hence, it is extremely difficult to provide a fuel spray foam formed by the fuel injected from each of the fuel injection bores of the primary and secondary groups, as desired.
Accordingly, it is an object of the present invention to provide a fuel injection valve designed so that a fuel spray foam formed by the fuel injected from each of the fuel injection bores of the primary and secondary groups can be provided easily as desired, while facilitating the formation of the fuel injection bores of the primary and secondary groups.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a solenoid-type fuel injection valve comprising a valve seat member having a valve seat and a valve bore provided through a center portion of the valve seat, a valve stem for opening and closing the valve bore by cooperation with the valve seat, an injector plate coupled to an outer end face of the valve seat member and having a plurality of fuel injection bores disposed around an axis of the valve bore, and a fuel diffusion chamber which is defined between the valve seat member and the injector plate and which is faced by the valve bore and all of the fuel injection bores, the plurality of fuel injection bores being parted on a plane including the axis of the valve bore into a primary group of fuel injection bores and a secondary group of fuel injection bores for injecting fuel toward a pair of primary and secondary intake ports, respectively, wherein the fuel injection bores of the primary group are formed so that they are inclined to a side opposite an away from the axis of the valve bore only in a direction X toward a downstream side, and the fuel injection bores of the secondary group are formed so that they are inclined to a side opposite and away from the axis of the valve bore only in the direction X toward the downstream side, wherein the direction X represents a direction of arrangement of the primary and secondary ports in the internal combustion engine, and a direction Y represents a direction perpendicular to the direction of arrangement.
With the first feature, the fuel injection bores of the primary and secondary groups are angled only in the direction X to provide spreading angles to primary and secondary fuel spray foams formed by the fuel flows injected from the primary and secondary fuel injection bores with respect to the axis of the valve bore, and the spreading angles of the primary and secondary other spray foams in the directions X and Y are determined depending on the axis distances between the fuel injection bores and the valve bore. More specifically, the angle of inclination of the axis of the valve bore is zero in the direction Y and hence, each of the fuel injection bores can be formed easily at a desired inclination angle in the injector plate by pressing or by drilling, only by inclining the injection plate and a tool relative to each other in the direction Y. Therefore, it is possible to easily provide the primary and secondary fuel spray foams formed by the fuel flows injected from the fuel injection bores of the primary and second groups, as desired, while facilitating the formation of the fuel injection bores of the primary and secondary groups.
According to a second aspect and feature of the present invention, in addition to the first feature, the fuel injection bores of the primary group are sub-classified into a primary inner group of fuel injection bores, and a primary outer group of fuel injection bores disposed on opposite sides of the fuel injection bores of the primary inner group in the direction Y at locations where an axis distance between the fuel injection bore of the primary outer group and the valve bore is smaller than that between the fuel injection bore of the primary inner group and the valve bore, and the fuel injection bores of the secondary group are sub-classified into a secondary inner group of fuel injection bores, and a secondary outer group of fuel injection bores disposed on opposite sides of the fuel injection bores of the secondary inner group in the direction Y at locations where an axis distance between the fuel injection bore of the secondary outer group and the valve bore is smaller than that between the fuel injection bore of the secondary inner group and the valve bore.
With the second feature, the spreading angles of primary and secondary fuel spray foams formed by the fuel flows injected from the fuel injection bores of the primary and secondary groups with respect to the axis of the valve bore are determined by the axis distances R between the fuel injection bores of the primary and secondary inner groups and the valve bore, and the angle of inclination of the fuel injection bores with respect to the axis of the valve bore. The spreading angles of the primary and secondary fuel spray foams in the direction X are determined by the axis distance between the fuel injection bores of the primary and second inner groups as well as the primary and second outer groups. Further, the spreading angles of the primary and secondary fuel spray foams in the direction Y are determined by the axis distance between the fuel injection bores located on the outermost side in the direction Y and the valve bore. Therefore, the number of factors for forming the primary and secondary fuel spray foams is reduced, and it is easy to form the primary and secondary fuel spray foams.
According to a third aspect and feature of the present invention, in addition to the second feature, the fuel injection bores of at least one of the primary and secondary outer groups are formed at a diameter smaller than that of the fuel injection bores of the corresponding inner group.
With the third feature, the spreading of tip end of the fuel flow injected from each of the outer fuel injection bores can be suppressed to a small extent by setting the diameter of each of the outer fuel injection bores at a small value, and hence, the spreading angles of the corresponding primary and secondary spray foams in the direction Y can be defined distinctly, thereby preventing the deposition of the injected fuel to a partition wall between the primary and secondary intake ports in the internal combustion engine to the utmost.
According to a fourth aspect and feature of the present invention, in addition to any of the first to third features, the total of cross-sectional areas of the fuel injection bores of the primary group is set larger than that of cross-sectional areas of the fuel injection bores of the secondary group.
With the fourth feature, the amount of fuel injected from the fuel injection bores of the primary group is larger than that of fuel injected from the fuel injection bores of the secondary group, and thus, in the internal combustion engine, it is possible to exhibit a fuel-dispensing characteristic suitable for the low-speed operational state in which the amount of gas drawn in the primary intake port is larger than that in the secondary intake port. This can contributes to an enhancement, particularly, in performance of the low-speed operation of a higher use frequency.
According to a fifth aspect and feature of the present invention, in addition to any of the first to fourth features, the relationship between the thickness t of the injector plate and the minimum diameter d of the fuel injection bores of the primary and secondary groups is set at t/d less than 1.
With the fifth feature, the atomization of the fuel injected from each of the fuel injection bores can be promoted, while reducing the function of restricting the direction of the fuel injected from each of the fuel injection bores. The setting of the spreading angles of the fuel spray foams depending on the axis distances R between the valve bore and the fuel injection bores can be achieved further easily and properly by reducing the function of restricting the direction of the fuel injected from each of the fuel injection bores. Thus, it is possible to achieve the proper setting of the spreading angles of the fuel spray foams and the promotion of the atomization of the injected fuel simultaneously.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.